Damper control system



July 28, 1942. M JOY 2,291,231

DAMPER CONTROL SYSTEM v Filed Dec. 4, 1940 dog T .B/ISEMENT 5g swam INVENTOR Hen 111. Jay BYa. 4e

ATTO R N EY Patented July 28, 1942 UNITED STATES PATENT OFFICE DAMPER CONTROL SYSTEM Henry M. Joy, Dayton, Ohio, assignor to The Master Electric Company, a corporation of Ohio 8 Claims.

This invention relates to an improved damper control system, and more particularly to a system wherein a furnace damper is automatically returned to a fire-retarding position upon a failure of the source supplying power to the control system.

An object of this invention is, broadly speaking, the provision of an improved system for the control of furnace dampers.

Another object of the invention is to prevent overheating of a furnace upon failure of the power source for the electric furnace control system.

Still another object of this invention i the provision of an improved damper control system for furnaces, wherein the damper is returned to the fire-retarding position upon failure of the source of control power, if the damper is in the fire-accelerating position at the time of such failure.

A further object of this invention is the provision of a furnace damper control system, wherein the damper i biased to the fire-retarding position and held in the fire-accelerating position in accordance with the call of a, controlling thermostat, by an electrical braking device connected across the source of control power.

A still further object of this invention is the provision of a safety furnace damper control system, wherein the furnace dampers will always be moved, if necessary, to their fire-retarding position upon the failure of the power source irrespective of the call of a temperature-responsive control or the position of a basement switch.

These and other features, capabilities and advantages of the invention will appear from the subjoined detailed description of one embodiment and a modification thereof, illustrated in the accompanying drawing, in which:

Fig. 1 is a circuit diagram of my novel control system, including details of the damper control mechanism;

Fig. 2 is a partially diagrammatic view illustrating a possible relationship between the damper control mechanism of the present invention in conjunction with a furnace damper; and

Fig. 3 is a partial detailed View of a modified motor switch used in conjunction with the control system illustrated in Fig. 1.

With particular reference to Fig. 1, the control system there illustrated embodies a dampercontrol mechanism generally indicated at Hi. This damper control mechanism preferably consists of an ordinary damper motor I 2 driving a gear train indicated at M, the latter, in turn, driving a damper arm l6 and a circuit control member such as a commutator l8. Suitable means such as spring 20 is used to bias the damper control lever to the position indicated in full lines, which position is intended to correspond to the off or fire-retarding position of the furnace damper (see Fig. 2). The motor is designed to rotate the lever arm I6 through the gear train M in the direction of the arrow R.

In the preferred form of the invention illustrated, the damper motor l2 and thus the furnace dampers are adapted to be controlled by the usual room thermostat, generally indicated at 22, although it will be obvious to those skilled in this art that such control may be effected in response to other temperature-responsive devices, depending upon the exact condition which it is desired to control. For the sake of convenience, the present invention will'be described in connection with control by a room thermostat. This thermostat may be provided with a well known preheating ignal lamp 23.

The control system of the present invention is preferably a low-voltage control system deriving its power from a source indicated at 24 through a suitable transformer 26, although it is to be pointed out that if the elements making up the instant control system are suitably designed, the control voltage is not critical and the usual line voltage could obviously be used.

As the system is illustrated in Fig. 1, all of the parts are in their off position. The room thermostat 22 does not call for heat and the furnace dampers are in their fire-retarding position. If, now, the room thermostat 22 calls for heat and moves to its on position, an energizing circuit will be established for the damper motor which may be traced from one side of the secondary winding 28 of the transformer 26, through conductor 30 to commutator brush 32, thence to the commutator l8 to the commutator brush 34, conductors 36 and 38 to contact 40 of the thermostat 22, thermostat arm 42, conductor 44, contact 46 and switch blade 48 of the basement switch 50,

and conductors 52 and 54 to one side of the motor l2. From the other side of the motor I 2 conductors 56 and 58 lead to the other side of the transformer secondary winding 28. Upon energiZatiOn, the motor l2 will drive the geartrain l4 and thus the damper lever IS in the direction R. At the same time, the commutator l8'is rotated in the same direction. As a result of the rotation of the commutator, the circuit for the motor [2 will be broken when the commutator arm 34 meets the open section 59 of the commutator I8, but before this happens the commutator arm 62 shown originally as out of contact with the commutator will meet the commutator I8 to establish a circuit for the damper motor independently of the position of the room thermostat 22. By this arrangement, it is assured that when the damper motor has started to move the damper lever I6 from the off to the on positions, this action will continue. The alternative circuit for the damper motor so established may be traced from the energized commutator arm 32, the commutator I8, the commutator-arm 62, and conductors 64 and 54 to the one side of the motor. However, when the damper motor has rotated to such an extent that the damper lever arm I6 has reached the on position, the circuit to the damper motor will be interrupted if the room thermostat is still in its on position as at this point the commutator arm 62 will meet the open commutator section 68.

If the damper motor has now moved the dampers to the on or fire-accelerating position, and the room thermostat is satisfied the latter will move to its off position and. establish a circuit for the damper motor to rotate the damper control lever in the same direction but from the on to the off position thereof. This circuit may be traced from the energized commutator arm 32 through the commutator I8 to the commutator arm 66 which will now be in contact with the latter. From this point the circuit extends through co-nductors 68 and I8 to the "off contact I2 of the thermostat 2-2 and thence through thermostat arm 42, conductor 44, contact- 46, switch arm 48 and conductors 52' and'54 to the damper motor I2. Again, after the damper motor has been once energized, it will continue to rotate until'it has completed its operation, despite the fact that: in the-meantime the'room thermostat may change its position. This isbrought about by the factthat' although the commutator arm 66' will quickly meet the open section 59 of the commutator as was true when, the-dampers moved from their off to their. on positions, a secondary circuit willbe established'through' the commutator arm 62 sothat movement from the on to the off positions is assured.

Irr thus'gerrerally above: describing the-control of the damper motor and dampers'by the: room thermostat 22, the action of the-biasing spring 26 was ignored. Obviously, if thedamper motor is de-energized when the leverarm I6 isin the on position the spring 20 would, unless some further means were provided, irmnediately return the lever I6 to the off position. To prevent this, a. suitable braking device generally'indicated at 14 is provided. In a' preferred embodiment of thisbraking device as illustrated, it' may consist of a toothed pivoted lever arm I6; adapted to' engage and therefore holdone ofthe' gears of the train I4, such as the pinion 'l8 The'lever arm I6 is normally held out of engagement with'the pinion I8 by suitable means" such as a spring indicatedat 80; but engagement'will result upon energization of the'winding 82 attracting one end of the lever arm. 16 and, as a result, causing engagement of the other end of the lever arm with the pinion I8. Energization of the winding 82 is preferably-controlled both by the position of the commutator I8 and by a suitable motor switch84- having normally closed contacts 86' and 88 which areopened in any suitable manner upon energization of the damper motor I2.

Various arrangements are known to the art whereby a switch may be moved in response to energization of a motor, and any of these are suitable, although a specific embodiment of such a construction has been illustrated in Fig. 3 and will be described in more detail hereinafter. However, as far as the novel system here disclosed is concerned, it can be assumed that any suitable switch may be used.

As was just stated, the contacts and 88 of the motor switch 84 are normally closed when the damper motor is not energized. This does not mean, however, that the brake coil 82 will be energized when the damper motor is not energized and the dampers are in their off or fireretarding position. In the off position of the system as illustrated in Fig. 1, the brake coil 82 will not be energized as its circuit must be completed through the commutator arm 66 which, as will be seen, in the off position of the lever arm I5 is not connected to the power source as it doesnot touch the commutator I8 but rather falls within the open section 59 thereof. However, when the damper motor has moved the lever arm I6 to the on position, through aircuitspreviously traced in connection with the operation of the damper motor it will be seen that the commutator arm 66- will be in contact with the commutator segment I8 and will thus be energized. In this case, when the damper motor reaches the on position and stops, an energizing circuit for the coil 82 may be traced from the commutator arm 66, conductors 68 and 90, closed contacts 86 and 88, and conductor 92 to one side of the coil 82. From the latter, conductors 98 and 58 lead to the other side'of the transformer secondary winding 28. By this means, when the damper motor I2 has moved the damper lever arm I6 to the on position, and is deenergized, the dampers will not return to the off position under the action of the spring 20 since the lever arm I6 will be held in the on" position by the brake mechanism I4. However, if the room thermostat moves to the off position to again energize the damper motor to move the lever arm I6 and the dampers from the on to the off positions, this movement is possible because energization of the motor I2 opens the motor switch 84 and thereby releases the brake.

It will be realized from a study of the system which has just been described that when the lever arm I6 is in its on position and the dampers, as a result are in their fire-accelerating positions, the only instrumentality which retains them in this position is the brake device I4 which, at that time; through the circuit previously traced will be connected to the source of power for the control system as a whole. In such a case if there occurs a failure of the power source for any reasons whatsoever, the coil 82 of the brake I4 will become deenergized and by the force of the biasing spring 20 the' lever arm I6 will be immediately returned to its off position in a direction opposite to that of the arrow R, and the dampers will accordingly be returned to their fire-retarding position. Thus a safety feature results inasmuch as a failure of the power supply will not as in many systems now known to the art, completely disable the damper control system and leave the dampers in the fire-accelerating position with the consequent danger of overheating and even conflagration. This safety feature which has been incorporated in my damper-control system does not in any way interfere with the normal operation of the furnace dampers by means such as the room thermostat, and will not affect the control system if the dampers are already in their fire-retarding position. Additionally, when power is restored, the system is immediately prepared to function without the necessity of any attendance upon the part of an operator.

Fig. 2 indicates more or less diagrammatically the manner in which a draft damper may be controlled by the damper mechanism shown in Fig. l. I have partially indicated a furnace at I04 showing its draft damper I96 in the closed or fire-retarding position. Obviously, the damper I06 will be open when the damper lever arm I6 moves from its oif to its on position through the interconnection by suitable means such as a rope or chain I08. Instead of controlling a normally closed draft damper Hit, the system may control a check damper which, to the contrary, will be normally open in the off position of the lever I5, or the latter may control both dampers at once, one then being normally closed and the other normally open.

It will also be apparent to those skilled in the art that the present system need not be limited to the control of dampers, but is readily adaptable to the control of any heat-retarding and heat-accelerating mechanism, where the control of such mechanism is effected in response to the amount of such heat and the danger of overheating upon failure of thecontrol power is to be avoided.

While as previously stated in connection with the description of the control system illustrated in Fig. 1 any type of motor switch 84 is suitable, which will open its normally closed contacts upon energization of the motor, I have shown in Fig. 3 a type of switch structure which is particularly suitable for this purpose. In this case, the switch 84' has normally closed contacts 86' and 88'. They are held normally closed by suitable means such as spring II 2, and the contact 86' will be attracted toward the motor I2 upon energization of the motor winding III), the contact 86 and its arm being attracted in this case by the magnetic field of the motor.

One of the features of the control system of the present invention is that it will operate to move the dampers to their fire-retarding position whether such dampers are opened in response to the call of a thermostat or in response to the operation of a basement switch. As is well known in the art a basement switch is desirable when stoking a fire to open the draft, even though the room thermostat may not call for heat. If the switch arm 48 of the basement switch 50 is moved from the contact 46 to the contact I90, a circuit will be established for the damper motor to move the damper lever arm I from the off to the on position and this circuit may be traced from one end of the transformer secondary winding 28, conductor so, contact arm 32, commutator I8, contact arm 34, conductors 36 and I02 to contact I00, and switch arm 43 through contacts 52 and 54 to one side of the motor I2. The operation of the damper motor will be the same as though the room thermostat moved to the on position. Similarly, the operation of the brake device I4 will be as previously described, the circuit for the coil 82 of the brake I4 being whollyindependent of the basement switch so that even though the latter may call for an on position of the damper motor lever I6, upon the failure of the power source the lever will be returned to its off position by the action of the spring 20.

It will accordingly be noted that the arrangement shown and described will serve admirably to accomplish the objects stated above. It is to be understood, however, that the arrangement disclosed above is intended merely as illustrative of the invention and not as limiting, as various modifications thereof including those already mentioned may be made without departing from the invention as defined by a proper interpretation of the claims which follow.

I claim:

1. In a furnace controlling system of the character described, in combination, a control member movable between heat-retarding and heataccelerating positions, a motor, means driven by said motor for moving said control member between said positions, means for biasing said driven means to the heat-retarding control member position, a source of power, temperature-responsive means controlling the energization of said motor from said source of power, means connected to said source of power when said motor and driven means are in the heat-accelerating control member position for holding said motor and driven means, whereby upon a failure of the source, of power at this time said driven means and control member will be returned to heatretarding position under the action of said biasing means, switch means having contacts biased to closed position and opened in response to energization of said'motor, and means for serially connecting said contacts with said holding means and source of power.

2. In a damper control system of the class including a source of power, a motor, a damper, means for moving said damper to the fire-retarding and fire-accelerating positions, a commutating device driven by said motor for controlling the energization and de-energization of the same, a single-pole thermo-responsive switch having on and off contacts, and conductors interconnecting said motor, commutating device and switch to said source of power for energizing said motor to move said damper to the fire-accelerating position when said switch is in its on position and to move said damper to the fireretarding position when the switch is in its ofi position, the combination of means for biasing said damper towards its fire-retarding position, and means connected for energization by said power source for holding the damper in its fireaccelerating position when the motor is de-energized, whereby when said damper is in its fireaccelerating position said biasing means will move it to the fire-retarding position upon the failure of said power source.

3. In a damper control system, in combination, a source of power, a damper movable between fire-retarding and fire-accelerating positions, an electrical device, means for connecting and disconnecting said electrical device with said source of power to energize and de-energize the same, mechanical means interconnecting said electrical device with said damper for moving the latter to said positions when said electrical device is energized, means for biasing said damper to the fireretarding position, and means connected to said power source for holding said damper when in fire-accelerating position when said electrical device is de-energized, whereby upon a power failure said biasing means returns said damper to its fire-retarding position.

4. In a damper controlling system, in combination, a source of power, a damper motor, a damper movable between fire-retarding and fire-accelerating positions, a gear train driven by said motor, a, lever arm drivenby'saidgear train and.

connected. to said damper for moving the same between said positions, a commutating device driven by said gear train, a temperature-respon sive'switch, conductors for connecting said motor to said source of power through said temperatureresponsive switch and said commutator for driving said gear train and lever arm to move said damper to the fire-accelerating position when said temperature-responsive switch calls for heat and to the fire-retarding position when said temperature-responsive switch is satisfied, means. on said commutator for disconnecting said motor from the source of power when the motor has reached one control position for the damper in response to one call of the temperature-responsive switch and simultaneously establishing a power circuit for the motor in dependence upon movement of the temperature-responsive switch for another call, means normally biasing said damper to the fire-retarding position, a device capable of holding said damper in the fire-accelerating position despite the de-energization of said motor and the action of said biasing means, an energizing coil for said device, and means for connecting said coil to said source of power only upon de-energization of said motor in the position corresponding to the fire-accelerating position of said damper.

5. The combination according to claim- 4, inwhich said last means includes a normally closed switch opened in response to the energization of said motor.

6; The combination according, to claim 4, in combination with a basement switch for energizing said motor from said source of power to move the same to a position corresponding to the fireaccelerating position of said damper, irrespective of the call of said temperature-responsive switch.

'7. The combination according to claim 4, in which said lever is moved by said motor and gear train less than from the corresponding fireretarding to the fire-accelerating positions of said damper and more than 180 from the fireaccelerating back to the fire-retarding positions, and said biasing means comprises a spring connected to said damper arm tending to return said lever to its fire-retarding damper position through the smaller are.

8. A damper motor unit for fiu'naces comprising, in combination, a motor, a gear train driven by said motor, a lever arm and motor-controlled circuit commutator driven by said gear train, an electrically energizable brake device for said gear train, and a switch having contacts biased to closed position and opened in response to energization of said motor, and means for serially connecting said contacts with said brake device.

HENRY M. JOY. 

